Can you Grow Your Own Peanuts?

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Q. I want to interest my grandson in gardening. Can I plant unshelled, untreated regular peanuts (say from Whole Foods) in a bed where I had potatoes three years ago? Thanks very much; you're our 'reliable source'!

---Glenna in Huntingdon Valley, PA

A. You can try growing peanuts, but I don't recommend starting with ones from a store—for several reasons.

Although peanuts are sold in raw form (and despite what you might hear, are relatively safe to eat uncooked, especially in small amounts), most packaged, store-bought peanuts are likely going to be treated in some way that makes them safer to consume but destroys their viability as seed stock. Roasted and boiled peanuts will, of course, be labeled as such. But unshelled and seemingly 'raw' peanuts may have undergone some type of heating or drying process to improve their shelf life and reduce the risk of a very dangerous type of mold to which peanuts are prone (more on this in a bit). No matter what, peanuts must have their thin skins intact to be viable as seed.
Peanuts take up a lot of garden space for a long time, and you maximize your chances of getting something edible at the end by planting guaranteed seed of a known type and variety.
There's a good chance that store-bought peanuts are going to be either standard "Virginia peanuts" or "runners". These types produce really large-sized 'nuts', but the varieties that are normally grown commercially need a really long growing season to mature—around 150 days of warm weather, which you won't get in a Pennsylvania summer. Heck, you'll have a hard time growing true Virginia peanuts in many parts of Virginia; they're really a crop for areas deeper in the South, like the Carolinas and Georgia. There are 'early' varieties that require less growing time, but store-bought peanuts might not be early types. And I always tend towards caution when a child's hopes risk being dashed—so…

Order fresh seed. If you have a reasonably long growing season (and want big 'nuts'), look for an early variety of Virginia peanuts. If you have a short season, seek out a type that demands much less growing time, like "Spanish", or red skinned peanuts (which require about 120 days of warm weather), and Valencias, some varieties of which are touted as being able to produce in as little as 90 days. (Early Valencias can allegedly be grown as far North as Canada.)

And although the vast majority of peanut seed is direct-sown after all chance of frost is gone, advanced gardeners who have the ability to successfully start their own healthy, stocky, good-looking plants from seed can gain a good 30 days by starting their peanuts indoors and transplanting them out when the soil is warm. You'd have to grow and plant them in peat pots or some other kind of 'plant the pot and all' contraption to avoid damaging the sensitive roots. And you really do have to know how to start healthy plants from seed indoors; garden soil and a "sunny windowsill" won't cut it.

…Neither will most garden soil outdoors. Peanuts are prone to a very dangerous mold known as aflatoxin, and one way to keep this nasty creature at bay is to have superb drainage in your soil. Growing peanuts in heavy clay is not advised. Were I to give this crop a try, I would mix a big bag of perlite or soil-free mix into one of my best-draining raised beds to really lighten it up.

…And then I'd be patient. The soil temperature must be at least 65° F. (measured at a depth of four inches), and night time air temps have to be 55° F. or warmer before you can plant seed in the ground directly. Planting in cold wet soil will virtually guarantee failure.

Now some good news: although we use them like tree nuts, peanuts are legumes. Like peas and beans, they have the ability to take plant-feeding nitrogen right out of the air we breathe. So if you want great yields and serious bragging rights, treat the seed with a peanut-specific inoculant; this natural bacteria will convey that 'nitrogen-fixing' power to the plant's roots.

Plant the inoculated seed—unshelled but with the fragile skin intact—an inch or two deep. If the soil tests acidic, add some lime or wood ash to it before planting; peanuts like a soil with a pH of 6.5 to 7 (and adequate calcium is important to getting quality 'nuts'). The plants will produce pretty yellow flowers that will then 'peg' or bury themselves in the soil, where they will produce the desired 'nuts' underground. So you can't use mulch—it prevents successful pegging. But you can spread a calcium-rich plant food (like one designed for tomatoes) on the surface of the soil mid-season. Cover it with a thin layer of compost to get it working fast.

Then, when you reach your variety's stated maturity date, pull up a sample plant and crack a few nuts; if they come off the plant easily and the inside of the shell is a dark color, they're ripe. Cure your harvest by spreading the 'nuts' out single-file in a bright, airy spot until they're dry enough to crack. Keep them dry and use them as quickly as possible. You can eat a few raw, but roasting or boiling is recommended. No matter what, discard any moldy-looking peanuts immediately and wash your hands well. That aflatoxin is a nasty actor.

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